In two distinct animal models of chronic renal failure phosphate restriction has been shown to be effective in preventing progressive functional deterioration. The fact that one of these animal models, antiglomerular basement membrane antibody disease, closely resembles human real disease in association with the finding of a similar pattern and amount of calcium-phosphate deposit in human and experimental end-stage kidneys strongly suggests that phosphate restriction might also be beneficial in humans with chronic renal failure. However, before this form of therapy could be used in man a number of important questions must be answered which is the purpose of this study. In order to deterime if P restriction is effective in all types of renal disease chronic renal failure animal models of glomerular, interstitial and vascular disease will be utilized. The effect of P restriction will be evaluated 1) by measuring renal function serially throughout the study period, 2) by performing routine renal histological, electromicroscopy and immunofluorescence studies, and 3) by analytical and biochemical means to study how renal inorganic and organic constituents are modified by this therapy. These studies will fully evaluate how much P restriction is necessary, when during the course of renal failure P restriction is effective and the toxicity of increased intake of P on the diseased kidney. Attempts to determine the mechanism by which P restriction is protective will be performed by looking at the role of PTH in this phenomenon, by determining if altering renal handling of P will effect renal damage and by evaluating the interrelationship between Ca and P in mediating this injury. Finally to determine if P restriction is effective in ohe species, studies will be performed in the dog as well as the rat.